Warning system with plural identification of signalling stations

ABSTRACT

A signalling system of the type with signalling devices stationed in protected premises and, upon actuation, transmitting a signal to a central receiving location. In the central receiving location, the system situates a plurality of zonal monitoring circuits, each of which is connected to and monitors a plurality of coded signalling devices forming a loop circuit. Each of the zonal monitoring circuits responds to reception of a coded signal by indicating through a first output path that a signal was received and by transmitting through a second output path the coded signal. At the receiving location, the receiver has an annunciator or indicator portion connecting with the first output paths of the zone circuits to indicate, for example by lighting a lamp, from which particular zone a signal originated. Also at the receiving location, a recorder portion is provided which connects in a loop with the second output paths of the zone circuits, and which both receives and records the coded signal, thereby providing a dual basis for positively identifying the location of a particular signalling device which has been actuated. In operation, the coded signalling devices provide a signal by opening their loop circuits. The zone circuits respond to this open circuit condition by de-energizing a relay which was energized through a loop circuit, which simultaneously removes a shunt placed across the zone circuit&#39;&#39;s second output path, closes a circuit through the first output path to provide an indication that a signal has been generated, and energizes a second relay which transfers the signalling device loop circuit into connection with the zone circuit loop for transmission of the coded signal to the recorder. When the coded signal is completed, a reset switch is closed to one again energize the first relay.

United States Patent Andrews Oct. 24, 1972 [54] WARNING SYSTEM WITHPLURAL IDENTIFICATION OF SIGNALLING STATIONS [72] Inventor: Clifton B.Andrews, North Pembroke, Mass.

[73] Assignee: The Proteetowire Co., Hanover,

Mass.

[22] Filed: April 29, 1971 [21] Appl. No.: 138,470

[52] US. Cl ..340/287, 340/293 [51] Int. Cl. ..G08b 25/00 [58] Field ofSearch ..340/164, 286, 216, 313, 409, 340/274, 287, 293, 420

[56] References Cited UNITED STATES PATENTS 3,500,377 3/ 1970 Meuther.....340/287 3,484,771 12/1969 Falck, Jr ..340/216 3,448,443 6/1969 Weld..340/287 3,150,359 9/1964 Hoey ..340/276 X 2,699,541 1/1955 Ward..340/293 3,540,043 11/1970 Crosthwait ..340/420 Primary Examiner-DonaldJ. Yusko Attorney-Sewall P. Bronstein, John D. Woodberry, Robert T.Gammons, Donald Brown, Robert L. Goldberg and Robert F. OConnell [57]ABSTRACT A signalling system of the type with signalling devicesstationed in protected premises and, upon actuation, transmitting asignal to a central receiving location. In the central receivinglocation, the system situates a plurality of zonal monitoring circuits,each of which is connected to and monitors a plurality of coded signalng devices forming a loop circuit. Each of the zonal monitoring circuitsresponds to reception of a coded signal by indicating through a firstoutput path that a signal was received and by transmitting through asecond output path the coded signal. At the receiving location, thereceiver has an annunciator or indicator portion connecting with thefirst output paths of the zone circuits to indicate, for example bylighting a lamp, from which particular zone a signal originated. Also atthe receiving location, a recorder portion is provided which connects ina loop with the second output paths of the zone circuits, and which bothreceives and records the coded signal, thereby providing a dual basisfor positively identifying the location of a particular signallingdevice which has been actuated.

In operation, the coded signalling devices provide a signal by openingtheir loop circuits. The zone circuits respond to this open circuitcondition by de-energizing a relay which was energized through a loopcircuit, which simultaneously removes a shunt placed across the zonecircuits second output path, closes a circuit through the first outputpath to provide an indication that a signal has been generated, andenergizes a second relay which transfers the signalling device loopcircuit into connection with the zone circuit loop for transmission ofthe coded signal to the recorder. When the coded signal is completed, areset switch is closed to one again energize the first relay.

10 Claims, 3 Drawing Figures [5.2 SWI CODE CODE RECORDER SOURCE lPATENIEDUET 2 m2 3. 701; 141

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7 Bl ZONEI Cl B2 ZONE 2 C2 R MONITORING 1 MONITORING I cone L2 CIRCUITCIRCUIT RECORDER l F 1? LZ|--- O z2 l ANNUNCIATOR J J cu t2; CODE g 15F2 SOURCE '6 Z/ISJ I a L.l

|s.| RYI 13 n if Bl c| Al GL2 Rc :l

CODE I I Q.) 'LZI RECORDER l 7: RA

INVENTOR 2 BYGjg Z (ll/F?Z LANZ REWS'Z ATTYS PATENTEB 3.701 141 sum: or2 FIGS BACKGROUND OF THE INVENTION The field of the present inventionrelates to signalling systems which station signalling devices in anarea to be protected, with signalssent to a central receiving locationwhich is to identify the particular device which has been used totransmit a signal. Such signalling systems are in common use as firealarms, burglar alarms, and various types of supervisory signallingservices.

Typical signal initiating equipment in sending stations of such systemsis set into operation either automatically, for example by the operationof a heat sensi- .is what enables assistance or corrective action to besupplied where itis needed.

As heretofore constructed, dual basis signalling systems have been ofthe type in which a signal originating in the protected premises issentthrough a pair of wires, arrives at the receiving location and there(a) activates a mechanism which supplies a code correlated to the pairof wires over which the signal is sent, which code is punched or printedto record the identify of the originating signal, and (b) activates anindicating lamp or annunciator drop to indicate the origin of thesignal.

This type of system has the very serious inherent defect that anincorrect signal will be indicated both in the coded record and by thelamp or annunciator drop if the pair of wires associated with thedesired signal is transposed with a pair of wires associated with someother protected premise. It can happen, therefore, that amisidentification of signal origin will occur and the signal system willsupply misleading information. While careful checking will reveal ifsuch a transposition has occurred, the signalling systems are sometimesmiles in length and checking is very cumbersome.

SUMMARY OF THE INVENTION Objects of the present invention are to providea signalling system which positively and reliably indicates the locationof the transmitting device, which easily permits detection of any errorin identification, which provides safe operation by giving a positiveindication if a circuit fault occurs, and which is inexpensive to makeand easy to use.

According to the invention, the signalling system for indicating at areceiving location the identity of a particular device in the protectedpremises which has been actuated to transmit a signal comprisesaplurality of zonal minitoring circuits, each of which monitors aplurality of signal devices located in the protected premises within aprescribed zone assigned to that circuit. The signalling devices are ofthe type which, upon actuation, transmit a unique coded signal to thezonal circuit. Upon receipt of a coded signal, the zonal monitoringcircuits respond through two separate outputs.

The zone circuits indicate through a first output path that a signal wasreceived and transmit through a second output path the coded signal. Atthe receiving station, an indicator means, such as an annunciator,connects with the first output paths of the zone circuits and indicatesfrom which particular zone a signal originated. Also at the receivingstation, a recorder means connects with the second output paths of thezone circuits and records the transmitted coded signal. Since. the codedsignal originates from the protected premises, it will always beindicated correctly at the receiving station and provides a checkagainst possible erroneous zone indications sent through the firstoutput paths and indicated by the annunciator.

In preferred embodiments, the coded signalling devices in each zone arein a loop circuit and signal by opening the circuit in a code pattern.The zone circuits have their second output paths connected in a loopwith the recorder means, and respond to opening of the signal deviceloop through relay means by connecting the signal device loop into thezone circuit loop for transmission of the coded signal to the recordermeans, and by closing contacts in the first output path to announce tothe indicator means that a coded signal has been received. In one highlypractical embodiment, the zone circuit has the winding of a first relayconnected in series with a power source through the signal device loop.The normally energized first relay has normally closed contacts shuntingthe second output path of the zone circuit and contacts for connectingpower to a second relay. The second relay has contacts that transfer thesignal device loop from its series connection with the first-relay, toconnection into the second output path of the zone circuit, which leadsto the recording means. Reset means are provided for restoring the zonecircuit to its initial condition, and test means are provided forsimulating a signal from a signalling device. The reset means'comprisesswitch means for temporarily energizing the first relay, and the testmeans comprises switch means for temporarily interrupting the circuitthrough the first relay winding and the power source. Preferably, thefirst relay winding is connected adjacent the ground tenninal of thepower source and the signal device loop is connected between the firstrelay winding and the positive terminal of the power source, so that afault in the signal device loop in the form of a ground, an opencircuit, or an open circuit with one side grounded, will result in asignal being sent to the receiving location.

These and other objects and novel aspects of the invention will beapparent from the following description of a preferred embodimentthereof.

DESCRIPTION OF THE DRAWING FIG. 1 is a diagram illustrating a signallingsystem ac- 3 DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustratesa signalling system S according to the invention and comprising, in acentral receiving lo cation, a receiver R with an annunciator portionRA, a

recorder portion RC, and a plurality of zone monitoring circuits Z1, Z2,etc. The zone monitoring circuits Z1, Z2, etc. respectively monitorcircuits L1, L2, etc., located in the protected premises and containingcoded signalling devices assigned to a respective circuits zone, withzone one circuit Z1 having in loop Ll the coded signalling devices C1.1,C1.2, etc.; loop circuit L2 of zone two circuit Z2 having coded signaldevices C2.1, C2.2, etc. The zone circuits Z1, Z2, etc., have firstoutput paths through terminals Al, A2, etc. leading to annunciator meansRA'with lamps LZl, LZ2, etc., for indicating from which particular zonea signal has originated. The zone circuits Z1, Z2, etc., also havesecond output paths through terminal pairs B1, C1; B2, C2; etc.,interconnected in series to form a zone circuit loop LZ with recordermeans RC, adapted to record the coded signals originating in the codedsignal devices and transmitted by the zone circuits. Since the codedsignal originates in the protected premises within the coded signaldevices, it is clear that the correct code will be transmitted torecorder means RC, and that any transposition which may occur in thelines forming loops L1, L2, etc., or in the lines from outputs Al, A2,etc., can be suitably detected by comparing the indication ofannunciator means RA with the indication of recorder means RC.

. FIG. 2 illustrates typical devices for the code signalling devices ofFIG. 1, and typical circuitry for the zone monitoring circuitsof FIG. 1,using zone circuit Z1 and code signalling devices C1.1 and C12 for thepurpose of illustration.

The coded signalling devices work on the principle of loop interruptionand have, as shown for device C1.2, a signalling contact spring 13normally touching and completing a circuit through two loop contactsprings 13.1 and 13.2, respectively. Contact spring 13 is positioned tobe lifted out of contact by means of a code wheel 14 made of brass orother conductive material and having a permanent connection 14.1 toground and, on its outer periphery, groups of coding teeth 14.2. Thewheel and coding teeth are normally separated out of electrical contact.As the wheel is rotated in a clockwise direction, contact spring 13touches the first tooth and grounds the loop Ll; with additionalrotation, the tooth 14.2 lifts spring,.13 away from contacts 13.1 and13.2 and the loop L1 is open circuited. The sequence of grounding of theloop and open circuiting of the loop is repeated for each tooth 14.2.

The code wheels of the signalling devices such as C1.2 are usuallyspring driven and they may be released either manually, mechanically orelectrically. It is to be understood, however, that the coded signallingdevices can operate at any desired manner so long as they provide theabove described opening of the loop L1 into which they are connected.

Zone monitoring circuit Z1 is supplied with a source of direct voltageconnected to terminals p and n, with the higher potential connected toterminal p and with terminal n grounded. The signalling device loop L1is connected inser ieswith the winding of a relay RYl and with thevoltage source connected to terminals p and n, through the normallyclosed switches 2.1 and 2.2 pro vided by a second relay RY2, through afuse F2, and through the normally closed contacts 15.2 of a manuallyoperated switch SW1 provided as described below for testing andresetting functions. Relay RYl is normally energized by current passingthrough uninterrupted loop L1, and has a switch 1.1 normally providing ashunt across output terminals 81 and C1, and a normally opened switch1.2 which, when closed, connects the voltage source at terminals p, nthrough the winding of relay RY2. In addition, switch 1.2, when closed,connects the voltage source at terminals p, n into output terminal A1which leads to the annunciator means RA, where an indicator lamp LZ1lights to announce the transmission of a signal from zone circuit Z1.Switches 2.1 and 2.2 of relay RY2connect signal device loop L1 either inseries with the winding. of relay RYl as indicated previously, or inseries with output terminals B1 and Cl which connect into the zonecircuit loop LZ which leads to the recorder means RC. I

The normal state of zone circuit 21 has signal device loop Ll intact,relay RYl energized, and relay RY2 deenergized. When a signal device,such as device C12, is actuated and opens signal device loop L1, thecircuit through the winding of relay RYl is interrupted and-the relayde-energizes. Switch 1.1 opens, to remove the shunt across outputterminals B1 and C1, and switch 1.2 closes to energize relay RY2 andlight lamp LZ1 located in the annunciator. means RA. Upon energizationof relay RY2, switches 2.1 and 2.2 disconnect loop L1 from relay RYland,connect it acrossoutput terminals B1 and C1. The foregoingoperations all take place upon the very first interruption of-loop L] bythe action of the first code'tooth 14.2. Assubsequent code teeth 14.2come into play, the coded signal is transmitted directly into zonecircuit loop L2, and the relays RYl and RY2 remain latched in theirrespective signalling states.

After a group of code signals has been transmitted from a device such asC1.2, zone circuit Z1 is restored to normal position by means of switchSW1. As indicated, switch SW1 has a toggle 15 pivoted at 16 and withnormally open resetting-contacts 15.1 providing an alternate seriesconnection of the voltage source at terminals p, n with the winding ofrelay RYl. By moving toggle 15 clockwise about its pivot 16, switchcontacts 15.1 are closed to temporarily reconnect relay RY1, throughfuse F1, to the voltage source. This results in the closing of switch1.1 to restore the shunt across terminals B1, C1 and'the opening ofswitch 1.2 to de-energize relay RY2 and lamp LZ1. When relay RY2 isde-energi'zed, switches 2.1 and 2.2 reconnect signal device loop L1between the relay RYl and the voltage source at terminals p, n, andrelay RYI is then energized through loop L1. Switch contacts 15.1 arethen opened and zonev circuit Z1 is ready to detect another signal fromloop .L1.

Switch SW1 also enables the interconnection of the zone circuits withthe receivers to be tested. As shown in FIG. 2, the energization path ofrelay RY1 includes normally closed contacts 15.2 of switch SW1. Whenopened by a counterclockwise rotation of toggle 15, the contacts 15.2provide an interruption in the energization circuit of relay RYl whichsimulates a similar interruption occurring in loop L1. While no codeaccompanies the interruption, the relays RYl and RY2 will switch as if asignal had been given, and lamp 121 will be lighted to show the testingof zone circuit Z1 and the indicia on annunciator means RA can becompared with the lighting of lamp LZl to ascertain if correctcorrespondence is provided by the wiring connections from outputterminals Al.

Relay RYl is connected adjacent ground terminal n and is separated fromthe positive terminal p by means of signal device loop L1. Accordingly,various faults occurring in loop Ll will be treated by the zone circuit21 as a signal, and an indication will be given in the central receivinglocation which can be traced back by means of annunciator means RA tolocate the source of the fault. For example, if loop L1 were to be opencircuited, the de-energization of relay RYl and ensuing switchoperations would take place. Similarly, if loop Llwere grounded, relayRYl would be shorted out, and its de-energization would result in asignal being sent to receiver R1. Similarly, a signal is given if loopL1 is broken and eitherside of the break is grounded. Thus, for allfault conditions in signal device loopLl, the zone circuit Z1 willprovide notification that a fault has occurred.

The signals sent through output terminals A1, A2, etc. from zone circuitZ1, Z2, etc. reach annunciator means RA where indicator lamps LZl, LZ2,etc., are lighted to identify the particular zone from which a signalhas been received. Accordingly, each lamp will have some mark toidentify the zone to which it corresponds. If there is any doubt thatthe indicated correspondence is correct, reference can be made to therecorder means RC which has received the coded signal. If desired, theindicating functions of the lamps LZl, etc. can be supplied byannunciator drops or the like.

A typical unit suitable for use as recorder means RC is illustrated inFIG. 3. As shown, recorder means RC has input terminals Br and Cr forconnection into the zone circuit loop LZ; and input terminals pr and nrfor connection to positive and ground terminals, respectively, of asource of direct voltage provided for energization of relays RY3, RY4,RY5, delay relay DRY6, and delay relay DRY7.

When the receiver R2 is in normal standby condition awaiting receipt ofa signal, the zone signal loop LZ forms a series circuit through thewindings of relays RY3 and RY4, the voltage source at terminals pr, nr,and normally closed relay switch 5.2, with the result that the relaysRY3 and RY4 are energized and relay switches 3.1 and 4.1 are open.

An alarm device 16 with a conventional code recording device 16.1 and anaudible signalling device such as single stroke bell 16.2 is connectedbetween ground terminal nr and positive terminal pr through twodifferent paths, one including relay switches 3.1 and 6.1, and the otherincluding relay switches 7.1, 4.1 and 5.3. The relay switches 6.1 and7.1 are normally closed, actuated by delay relays DRY6 and DRY7.

The recorder means RC has a safety circuit Sa which includes relay RYS,a heating resistor 26, a bimetal strip 27 actuating switch 27.1, andfault indicator lamp F. A resetting push-button switch 30 is alsoprovided.

The operation of recorder means RC takes place in the following manner.In normal operation, without faults, the recorder means RC responds tothe receipt of a code signal, appearing as an opening in zone circuitloop 12, by de-energizing relays RY3 and RY4, and closing switches 3.1and 4.1 thereby actuating alarm 16 and recording the circuit opening oncode recording device 16.1. Delay relays DRY 6 and DRY7 delay theopening of their switches 6.1 and 7.1 to permit recorder 16.1 tooperate. Each opening and closing of the code signal device results inthe energization and de-energization of relays RY3 and RY4 withattendant recording in recorder 16.1. In this manner recorder means RCprovides a record of the particular code signal received, which can becompared with the indication given by annunciator means RA to ascertainthe integrity of the system.

Recorder means RC makes use of its safety circuit to counteract variousfault conditions. For example, if zone circuit loop LZ is broken, butnot grounded, signals can be sent as a result of the differentconnections set up by the energization of relay RYS after the fault hasexisted for a time interval causing bimetal switch 27.1 to close.Similarly, the safety circuit handles a fault in the form of a groundwithout a break in the zone loop LZ, or a break occurring simultaneouslywith a ground. As a result, the signalling system is able to continueoperation over an extended range of conditions and its reliability isconsiderably enhanced.

It should be understood that the present disclosure is for the purposeof illustration and that this invention includes all modifications andequivalents which fall within the scope of the appended claims.

I claim:

1. A signalling system for indicating at a central receiving locationthe identify of a particular device in remote protected premises, whichdevice has been actuated to transmit a signal, comprising a plurality ofindependent zonal monitoring circuits at said central receivinglocation, each of said zonal monitoring circuits being connected throughseparate connecting 'paths to a selected plurality of said signaldevices located in said protected premises within a prescribed zoneassigned to each said zonal monitoring circuits for monitoring saidselected plurality of signal devices;

each of said signal devices upon actuation having means for transmittinga unique coded signal to its assigned zonal monitoring circuit;

each of said zonal monitoring circuits having means responsive toreception of a coded signal for indicating through a first output paththat a signal was received and for transmitting through a second outputpath the coded signal; and

at the receiving location, indicating means connecting with the firstoutput paths of said zonal circuits for indicating the particular zonefrom which a signal originated, and recording means connecting with thesecond output paths of said zonal circuits for recording the transmittedcoded signal.

2. A signalling system according to claim 1 wherein the signal devicesin a prescribed zone are connected in a signal device loop with itsassigned zonal monitoring circuit and transmit a signal by opencircuiting said loop, the zonal monitoring circuits each having relaymeans responsive to open circuitry of said loop to close a relay switchin the first output path, the indicating means comprising for each zonean indicator device energized by the closing of said relay switch forthat zone.

3. A signalling system according to claim 2 wherein said relay means islatched by the open circuiting of said signal device loop to maintainsaid relay switch closed, and wherein each zonal citcuit has reset meansfor restoring said relay means to a standby condition.

4. A signalling system according to claim 1 wherein said signal devicesin each zone are connected in a signal device loop with the assignedzonal monitoring circuit, the zonal circuits have their second outputpaths connected in a zone circuit loop with said recording means, eachzone having means for shunting said zone circuit loop, thereby toprevent interference with other zones, said zonal monitoring circuittransmitting said coded signal by removing said shunt and connectingsaid signal device into said zone circuit loop.

5. A signalling system according to claim 4 wherein said zonalmonitoring circuits have relay means responsive to receipt of a codedsignal, with relay switches connecting said signal devices into saidzone circuit loop, said relay means latching upon receipt of a signal,said zone monitoring circuit having reset means to restore said relaymeans to standby condition.

6. A signalling system according to claim 4 wherein said signal deviceloop is connected in series with a power source and the winding of anormally energized first relay means through a pair of relay switches ofa normally de-energized second relay means, said pair of relay switcheshaving a second position connecting the signal device loop into saidzone circuit loop when said second relay means is energized; the firstrelay means having a normally open relay switch for connecting the powersource through the winding of the second relay means, and a normallyclosed relay switch for shunting the zone circuit loop at said secondoutput path;

whereby when said signal device loop is open cir'cuited, said firstrelay means de-energizes, thereby removing the shunt from the zonecircuit loop and energizing the second relay means, said second relaymeans transferring said signal device loop to said zone circuit loop anddisconnecting said first relay from the power source.

7. Signalling device according to claim 6 wherein the normally openrelay switch of said first relay means connects said power sourcethrough said first output path to thereby actuate said indicating means.

8. Signalling system according to claim 6 wherein said zonal circuitfurther comprises reset means for restoring the zone circuit to normalcondition after a coded signal has been transmitted and said signaldevice loop is closed, said reset means comprising a switch temporarilyconnecting said power source through the winding of said first relaymeans to energize it, thereby returning the shunt to the zone loop,deenergizing the second relay means, and shifting said pair of relayswitches to reconnect the signal device loop in series with the powersource and first relay means winding.

9. Signalling system according to claim 6 wherein each zonal circuitfurther comprises testing means for simulating the transmission of asignal from said signal devices, comprising switch mea ns fortemporarily disconnecting said power source rom the winding '0 saidfirst relay means.

10. A signalling system according to claim 6 wherein said power sourcehas a positive terminal and a ground terminal, the winding of the firstrelay means is connected adjacent said ground terminal, the signaldevice loop is connected through said pair of relay switches betweensaid positive terminal and said first relay means winding, whereby aground, open, or open with ground occurring in said signal device loop,all will cause said first relay means to become de-energized and causesaid zonal circuit to react as if a signal had been given.

1. A signalling system for indicating at a central receiving locationthe identify of a particular device in remote protected premises, whichdevice has been actuated to transmit a signal, comprising a plurality ofindependent zonal monitoring circuits at said central receivinglocation, each of said zonal monitoring circuits being connected throughseparate connecting paths to a selected plurality of said signal deviceslocated in said protected premises within a prescribed zone assigned toeach said zonal monitoring circuits for monitoring said selectedplurality of signal devices; each of said signal devices upon actuationhaving means for transmitting a unique coded signal to its assignedzonal monitoring circuit; each of said zonal monitoring circuits havingmeans responsive to reception of a coded signal for indicating through afirst output path that a signal was received and for transmittingthrough a second output path the coded signal; and at the receivinglocation, indicating means connecting with the first output paths ofsaid zonal circuits for indicating the particular zone from which asignal originated, and recording means connecting with the second outputpaths of said zonal circuits for recording the transmitted coded signal.2. A signalling system according to claim 1 wherein the signal devicesin a prescribed zone are connected in a signal device loop with itsassigned zonal monitoring circuit and transmit a signal by opencircuiting said loop, the zonal monitoring circuits each having relaymeans responsive to open circuitry of said loop to close a relay switchin the first output path, the indicating means comprising for each zonean indicator device energized by the closing of said relay switch forthat zone.
 3. A signalling system according to claim 2 wherein saidrelay means is latched by the open circuiting of said signal device loopto maintain said relay switch closed, and wherein each zonal citcuit hasreset means for restoring said relay means to a standby condition.
 4. Asignalling system according to claim 1 wherein said signal devices ineach zone are connected in a signal device loop with the assigned zonalmonitoring circuit, the zonal circuits have their second output pathsconnected in a zone circuit loop with said recording means, each zonehaving means for shunting said zone circuit loop, thereby to preventinterference with other zones, said zonal monitoring circuittransmitting said coded signal by removing said shunt and connectingsaid signal device into said zone circuit loop.
 5. A signalling systemaccording to claim 4 wherein said zonal monitoring circuits have relaymeans responsive to receipt of a coded signal, with relay switchesconnecting said signal devices into said zone circuit loop, said relaymeans latching upon receipt of a signal, said zone monitoring circuithaving reset means to restore said relay means to standby condition. 6.A sigNalling system according to claim 4 wherein said signal device loopis connected in series with a power source and the winding of a normallyenergized first relay means through a pair of relay switches of anormally de-energized second relay means, said pair of relay switcheshaving a second position connecting the signal device loop into saidzone circuit loop when said second relay means is energized; the firstrelay means having a normally open relay switch for connecting the powersource through the winding of the second relay means, and a normallyclosed relay switch for shunting the zone circuit loop at said secondoutput path; whereby when said signal device loop is open circuited,said first relay means de-energizes, thereby removing the shunt from thezone circuit loop and energizing the second relay means, said secondrelay means transferring said signal device loop to said zone circuitloop and disconnecting said first relay from the power source. 7.Signalling device according to claim 6 wherein the normally open relayswitch of said first relay means connects said power source through saidfirst output path to thereby actuate said indicating means. 8.Signalling system according to claim 6 wherein said zonal circuitfurther comprises reset means for restoring the zone circuit to normalcondition after a coded signal has been transmitted and said signaldevice loop is closed, said reset means comprising a switch temporarilyconnecting said power source through the winding of said first relaymeans to energize it, thereby returning the shunt to the zone loop,de-energizing the second relay means, and shifting said pair of relayswitches to reconnect the signal device loop in series with the powersource and first relay means winding.
 9. Signalling system according toclaim 6 wherein each zonal circuit further comprises testing means forsimulating the transmission of a signal from said signal devices,comprising switch means for temporarily disconnecting said power sourcefrom the winding of said first relay means.
 10. A signalling systemaccording to claim 6 wherein said power source has a positive terminaland a ground terminal, the winding of the first relay means is connectedadjacent said ground terminal, the signal device loop is connectedthrough said pair of relay switches between said positive terminal andsaid first relay means winding, whereby a ground, open, or open withground occurring in said signal device loop, all will cause said firstrelay means to become de-energized and cause said zonal circuit to reactas if a signal had been given.